Brake actuating system

ABSTRACT

The present invention is a brake actuating and brake system for maintaining a predetermined proportional relationship between the rotational speeds of vehicle wheels by both applying and/or releasing hydraulic fluid brake pressure, and distributing released pressure back into the brake system.

This is a continuation-in-part of application Ser. No. 463,708, filedFeb. 15, 1974, now abandoned, which was a continuation of applicationSer. No. 74,118, filed Sept. 21, 1970, now abandoned which was acontinuation of application Ser. No. 603,334 filed Dec. 20, 1966, nowabandoned.

This invention relates to a brake system and more particularly to abraking system which operates as a function of the proportionalrelationships between the rotational speeds of vehicle wheels.

An object of the present invention is to provide a system which willdetermine the proportional relationship between rotational speeds of twoor more wheels of a vehicle.

Another object of the present invention is to provide a system which,upon sensing the proportional relationship between wheel speeds, willperform a braking function in a predetermined manner.

Another object of the present invention is to provide a system whichwill maintain predetermined speed proportions between driving wheels orshafts of a vehicle.

A still further object of the present invention is to provide a systemwhich will prevent skidding of a vehicle.

A further object of the present invention is to provide a brake systemwhich will increase a vehicle's ability to progress on a surface havingunfavorable traction properties.

The present invention fulfills the aforementioned objects and overcomeslimitations and disadvantages of prior art solutions of problems knownin the art by providing a brake system wherein speed detection meanselectrically sense the rotational speed of a moving part in a machine orvehicle, such as a wheel. The sensed information is electricallycommunicated to brake means which either apply or release fluid brakepressure as a function of the information received relating to therotational speed of the moving part. In the case where the systemattempts to slow down the rotational speed of the part or wheel, brakepressure is increased and braking forces are exerted such that the partor wheel is slowed. On the other hand, for the case where the systemattempts to increase the rotational speed of the part or to minimizedeceleration thereof, hydraulic braking pressure is released. In thislatter mode, the invention provides for conserving and redirecting thebrake pressure released from one or more wheels and redirects this brakepressure back into the brake system for increasing the brake pressure tothe other wheels.

In this last respect the invention is particularly useful in fluid brakesystems, where the conventional systems in anti-skid devices, forinstance on air-brake vehicles, such as trucks and buses, are presentlydesigned to release air pressure from the brake system to the atmospherewhen a reduction in braking effort is required. Such release of pressuremay occur more often than once per second. To maintain system pressure,it has been necessary to install larger, more expensive air compressorson vehicles which have anti-skid air brake systems. The presentinvention does not relieve brake effort by venting air pressure; thedevice instead conserves and redirects air pressure in an air brakesystem. Thus a further advantage of the invention is that smaller,lighter, and less costly air compressors may be installed, points ofconsiderable utility to operators of the commercial vehicles which relyon air brakes.

Similarly, in conventional anti-skid hydraulic brake systems provisionis made for closing off the addition of further liquid pressure to askidding wheel and for permitting the brake cylinder from which pressurehas been released to retract slightly but no provision is made forredistribution of brake pressure relieved at one wheel to the otherwheels as does the present invention.

A constant pressure at each brake circuit may cause one or more wheelsto "lock up" because one or more wheels have less traction on the roadsurface than do other wheels on the vehicle. The effect of anti-skidsystems is to interrupt or reduce the application of brake pressure atthe "locked-up" wheel. However, other anti-skid brakes tend either tobleed off and store fluid pressure applied by the driver, reducing theoverall braking effort intended, or to automatically throw the vehicleinto a full panic-stop mode not intended or needed. The latter action ofthe anti-skid brakes required by new law for trucks has createdconsiderable opposition on the part of truck drivers.

Therefore, it is a further object of the invention to provide ananti-skid system wherein braking effort is automatically redirected tothose wheels with superior traction, so that the overall braking effortintended by the operator is safely maintained and not artificiallyreduced or increased.

The invention will be more clearly understood from the followingdescription of specific embodiments of the invention together with theaccompanying drawings in which:

FIG. 1 is a schematic illustration of an electrical circuit arrangementcapable of being used with the present invention;

FIG. 1A is a schematic representation of a portion of the circuit shownin FIG. 1 with the addition of elements of the present invention;

FIG. 2 is a fragmentary elevation view of a vehicle axle and theassociated elements of the present invention;

FIG. 3 is a fragmentary plan view of the axle shown in FIG. 2;

FIG. 4 is a view taken along the line IV--IV of FIG. 2.

FIG. 5 is a view taken along the line V--V of FIG. 2;

FIG. 6 is a schematic illustration of an electrical circuit of anotherembodiment of the present invention; and

FIG. 7 is a diagrammatic illustration of a valve structure particularlyadaptable for use in the invention.

Referring now to FIG. 1 in which a circuit is shown in schematicarrangement with respect to the front and rear wheels of a vehicle inwhich the present invention may be utilized, front wheels 1 and 2 andrear wheels 3 and 4 are spaced in a manner as they would be if mountedon an automobile. A conventional automobile braking system may be usedand slightly modified with the present invention, and thus brake drums,discs and a hydraulic system with brake balancing may be used. Signalgenerators 5, 6, 7 and 8 are associated with each wheel 1, 2, 3 and 4,respectively, in such a manner as to indicate the wheel speed via asignal.

Assuming signal generators 5, 6, 7 and 8 to be of the alternatingcurrent type, and referring now to signal generator 5 in particular,conductors 9 and 10 are electrically connected to a circuit arrangement11, shown to be surrounded by dotted lines. Circuit arrangement 11consists of resistors R1 and R2, capacitors C1 and C2, and diodes D1, D2and D3 shown schematically in FIG. 1 and adapted to convert thealernating current signal generated by generator 5 into a direct currentsignal.

Emerging from the output side of circuit arrangement 11, conductors 12and 13 are indicated. Referring now to signal generator 6, conductors 14and 15 are shown leading from the alternating current generator 6 tocircuit arrangement 16 containing resistors R3 and R4, capacitors C3 andC4, and diodes D4, D5 and D6. Circuit arrangement 16 will convert thealternating current signal carried by conductors 14 and 15 into a directcurrent signal carried by conductors 17 and 18 at the output portion ofcircuit arrangement 16.

Referring now to the electrical circuit associated with rear wheels 3and 4, conductors 19 and 20 carry an alternating current signalgenerated by generator 7 and are electrically connected to circuitarrangement 21, which circuit arrangement contains resistors R5 and R6,capacitors C5 and C6, and diodes D7, D8 and D9. Circuit arrangement 21is adapted to convert the alternating current signal carried byconductors 19 and 20 into a direct current signal carried by conductors22 and 23 at the output portion of circuit arrangement 21.

Referring to signal generator 8, conductors 24 and 25 carry analternating current signal from signal generator 8 to circuitarrangement 26 which, in turn, contains resistors R7 and R8, capacitorsC7 and C8, and diodes D10, D11 and D12. Thus, as in the case for circuitarrangements 11, 16 and 21, circuit arrangement 26 converts analternating current signal into a direct current signal carried byconductors 27 and 28 at the output portion thereof.

Output signals carried by conductors 12, 17, 22 and 27 are fed throughresistances 29, 30, 31 and 32 respectively. It is to be noted that onceterminals 33 and 34 are connected by line 37, and since terminals 35 and36 are connected by line 38 and further, since lines 37 and 38 arejoined by line 39, terminals 33, 34, 35, and 36 of resistances 29, 30,31 and 32 are at substantially the same potential.

Also, the outputs carried by conductors 13, 18, 23 and 28 are atsubstantially the same potential due to their being interconnected byline 40.

A capacitance, designated by numeral 41, is situated between lines 39and 40 and is charged up to the potential of line 39 which, in turn isthe potential of the generated signal. The purpose of the presence ofthe capacitance 41 in the circuit is to cause a discharge throughresistances 29, 30, 31 and 32 when direct current signals decreaseslowly, as would be the case during braking of wheels 1-4 in the absenceof a skid condition. For the case where any of wheels 1-4 are skidding,the signal generated by the respective wheel or wheels will fall veryrapidly. However, the wheels that are not skidding will continue togenerate a signal and thus the line voltage of line 39 will assume avoltage substantially proportional to the vehicle wheel(s) speed, andthus a large voltage will exist across the resistance associated withthe skidding wheel. More specifically, if wheel 1 is in a skiddingcondition, a large potential will exist across resistance 29, thispotential providing a signal which is fed to another part of the overallcircuit to be described below.

It is within the scope of the present invention to provide means foramplifying the signals obtained as heretofore described and thus,amplifying means 42, 43, 44 and 45 are provided for the signals producedand associated with wheels 1, 2, 3 and 4.

Amplifying means 42 receives signals generated by signal generator 5 andconverted into DC signal carried by conductor 12 via line 46 whichelectrically connects conductor 12 with the input portion of amplifyingmeans 42. Similarly, the signal carried by conductor 17 is fed intoamplifying means 43 via line 47. The signal carried by conductor 22 isfed into the input portion of amplifying means 44 via line 48; and thesignal carried by conductor 27 is fed into the input portion ofamplifying means 45 via line 49.

The output of amplifying means 42 is fed to line 52 via line 50, whilethe output of amplifying means 43 is fed to line 52 via line 51. Line 52is connected to the circuit of valve VR which controls the distributionand pressure of hydraulic fluid being fed to the brakes in wheels 3 and4.

The output of amplifying means 44 is fed to line 55 via line 53, whilethe output of amplifying means 45 is fed to line 55 via line 54. Line 55is connected to the circuit of valve VF which controls distribution andpressure of hydraulic fluid being fed to front wheels 1 and 2.

The hydraulic linking of valve VF with wheels 1 and 2 is schematicallyshown by dotted lines 56 and 57, and similarly dotted lines 58 and 59show the hydraulic linkage of valve VR with wheels 3 and 4 respectively.The mechanical operation of this portion of the apparatus will bedescribed in more detail below.

Referring now to FIG. 1A, compensating means 60 is shown to beelectrically connected to conductors 19 and 20 associated with wheel 3,and conductors 24 and 25 associated with wheel 4. Compensating means 60is connected to valve VR and solenoid means 61 such that, underpredetermined conditions, a signal is sent to solenoid means 61 andvalve VR and hydraulic brake fluid is compressed by means of solenoidmeans 61 and fed to a wheel to be braked or slowed down.

Referring now to FIG. 6, it is seen that in another embodiment of thesystem shown in FIG. 1 valves VR1, VR2, VF1 and VF2 are associated withwheels 3, 4, 1 and 2 respectively, thereby enabling the user of thepresent invention to influence the rotational speed of each wheelindependently, as opposed to the system shown in FIG. 1 wherein valve VFinfluences wheels 1 and 2 simultaneously, and wherein valve VRinfluences wheels 3 and 4 in the same manner.

In FIG. 6, conductors 85 and 86, 87 and 88, 89 and 90, and 91 and 92 areconnected to the output of amplifying means 42, 43, 44 and 45respectively. Conductors 85 and 86 are electrically connected to valveVR1; conductors 87 and 88 with valve VR2; conductors 89 and 90 withvalve VF1 and conductors 91 and 92 with valve VF2. Therefore, viahydraulic lines 93, 94, 95 and 96, valves VF1, VF2, VR1 and VR2 controlwheels 1, 2, 3 and 4 respectively.

In this embodiment of the invention, a valve which is showndiagrammatically in FIG. 7 can be used to control braking pressure ateach wheel. Similarly, valves such as shown in FIG. 7 can beincorporated in valves VF and VR diagrammatically depicted in FIG. 1.

In any event, valve 100 comprises a cylinder 101, main piston 102 andsliding piston 109 together with communicating lines from and to a wheelbrake circuit 103; from and to the brake pedal 104 and an elbow section105 communicating above and below the main piston 102. Rod 106 connectsthe main piston 102 and the arm 107 to the actuating solenoid.

The sliding piston 109 is loosely fit about the rod 106 and spring 108retains the sliding piston and main piston apart.

A fluid seal, not shown, is provided between the arm 107 and valvehousing 101 so that the loose fit of the sliding piston on rod 106 willnot result in leakage.

FIG. 7 diagrammatically shows the valve in the normal position in whichbraking fluid is pressurized in lines 103, 104 and 105.

When the signal from the circuitry disclosed causes arm 107 and mainpiston 102 to move downwardly in response to the requirement for alimited slip differential effect, the main piston passes the bottom ofelbow section 105 and then compresses the fluid beneath main piston 102.This compression of fluid causes a pressure increase in the line 103 tothe brake circuit of the slipping wheel. When arm 107 retracts, slidingpiston 109 lags as the main piston recovers toward normal positionurging the sliding piston via spring 108 upwardly. The purpose of thesliding piston is to prevent surge in the main brake reservoir whichwould otherwise result from vacuum and then pressure created when themain piston goes down and then upward.

Importantly, when the signal directs the arm 107 upwardly resulting inthe upward movement of main piston 102, an anti-skid pressure-releasesituation, fluid pressure is relieved from the affected brake circuit tothe extent main piston 102 moves upward. Sliding piston 109 cannot movefurther upward; therefore, the distance between main piston and slidingpiston is reduced. The effect is to further compress the fluid betweenthese two pistons and force fluid pressure out through line 104. Eventhough line 104 is already pressurized by the brake pedal, the upwardmovement of main piston 102 causes an increase in pressure, via 104 tohydraulic lines to other wheels, that is proportional to the relief atthe "locked-up" wheel. Thus, the overall braking effort intended by thedriver is maintained, unlike other systems which override the driver'sdesired braking effort.

Thus it is seen that when a vehicle containing the present invention istraveling at a uniform speed, generators 5, 6, 7 and 8 will put outsignals which are substantially the same. Capacitance 41, after a finitelength of time, will reach the potential of the converted signalsthrough resistances 29, 30, 31 and 32. If the vehicle is slowed during anormal braking operation in the absence of skidding, the direct currentsignals, as described above, will decrease slowly, such that a dischargeof capacitance 41 will occur through resistances 29, 30, 31 and 32.Should one or more wheels assume a skidding condition, the directcurrent signal associated with the skidding wheel will decrease rapidlydue to the lower or nil rotational speed of the wheel, and due to thenon-skidding rotational condition of the remaining wheels, the potentialat the respective terminals (any of terminals 33, 34, 35 and 36) will beproportional to the speed of the vehicle. It can be seen that a largepotential will exist across the resistance associated with the skiddingwheel. This potential is sensed and fed through the amplifying meansassociated with the skidding wheel, resulting in actuation of theappropriate valve, which valve will selectively release brake pressurein a predetermined manner and proportionately transmit the increasedpressure from the skidding wheel via valve 100 to the other wheels.

In order that the operation of the elements of FIG. 1A does notinterfere with the operation of the elements of FIG. 1, a switch (notshown) of a known type is installed such that depression of the brakepedal or other member will engage the circuit of FIG. 1 and disengagethe circuit of FIG. 1A. When the brake pedal is not depressed, thecircuit of FIG. 1A is operative and that of FIG. 1 is inoperative.

In addition to the operation described in the preceding paragraph, thepresent invention is capable of increasing hydraulic fluid brakepressure to any one or more of wheels 1, 2, 3 and 4, the rotationalspeed of which is sought to be decreased. In the event the vehicle issituated on a surface such that one driving wheel is on a slipperysurface and the other is on a surface possessing good tractionproperties, the wheel on the slippery surface will tend to spin, whilethe other wheel will have a rotational speed substantially zero.Compensating means 60 will receive a substantially low signal from thewheel which is not turning and will receive a substantially strongersignal from the wheel that is spinning. Compensating means 60,responding to the signal, will then electrically actuate solenoid means61 which, in turn, will apply fluid brake pressure to the wheel which isspinning on the slippery surface, thereby slowing the spinning wheel andincreasing the overall traction properties of the vehicle.

It is contemplated and with the scope of the present invention toprovide such a system for machinery other than vehicles having rotatingparts, and it is further contemplated that the present invention havingapplication and be utilized in vehicles which are sea-going or airbound.

Referring now to FIG. 2, a rear axle housing 70 is shown in an elevationview as an example of the type of structure associated with conventionalautomobiles. The outline of a tire 71 is shown in dotted lines to beconcentric with brake housing 72. A portion of a flexible hydraulicfluid line 73 is shown communicating with a distributing unit 74, whichmay be of the conventional type. Hydraulic lines 75 extend fromdistributing unit 74 and communicate with solenoid activated valves 76and 77. From valves 76 and 77, hydraulic lines 75 feed the braking unit(not shown) in brake housing 72.

Within rear axle housing 70, rear axle 78 is free to rotate and hassecured to the periphery thereof at least one strip of magnetic tape 79,shown in FIGS. 2 and 4. Sensing units 80 and 81 are secured to rear axlehousing 70 adjacent the portion of rear axle 78 having the magnetic tape79 mounted thereon. Sensing units 80 and 81 may be of conventionaldesign and are adapted to detect and sense the rotational speed of rearaxle 78. This information is transmitted to portions of the circuitshown in FIG. 1 via conductors 82, for example, shown in FIG. 4.Similarly, information from the circuit shown in FIG. 1 is transmittedto the solenoid activated valves 76 and 77 via wires 83, shown in FIG.5. In a preferred embodiment of the present invention, sensing units 80and 81 may be mounted to rear axle housing 70 by bolts 84; however, itis within the scope of this invention to provide for other fasteningmeans and different element locations.

Reference to lines 37-40 and 46-55, of course, refers to conductors or"lines" of electrically conductive material.

The embodiments of the invention particularly disclosed are presentedmerely as examples of the invention. Other embodiments, forms andmodifications of the invention coming within the proper scope of theappended claims will of course readily suggest themselves to thoseskilled in the art.

It is within the scope of the present invention to provide apparatus toinsure that rotational speeds of members driven through a differentialremain within any desired proportional relationship. By varying thebehavioral characteristics of the elements, such as the valves,resistors, line sizes, etc., it is possible and contemplated toaccomplish predetermined and selected present conditions. The presentapparatus also makes it possible for the operator of a vehicle to varythese proportions and speeds at his discretion, or for the variations tooccur automatically, dependent on operations of another part of themachine, such as the turning of a steering gear. In some embodiments ofthe present invention, the apparatus is electro-hydraulic, and isinstalled outside the differential, acting on existing vehicle brakingsystems or upon specially added braking systems. Furthermore, thepresent apparatus may be installed by an automobile dealer after theassembly of the vehicle.

It is also within the scope of the present invention to provide afail-safe device having two pick-ups adjacent a conductor such that,should either of the pick-ups or the conductor fail, the solenoid wouldnot act. If one wheel's electrical circuit were to break or if theconductor fastened on the brake should dislodge, the system would workto brake the other wheel, in the absence of the fail-safe device.

Furthermore, it is within the scope of the present invention to havemagnetic tape or other means secured to a brake drum or disc, or to havemagnetic tape disposed in another suitable location.

What is claimed is:
 1. In a vehicle having at least four wheels at leasttwo of which wheels may be non-driven and any one or more of whichwheels which are driven may assume an overspeeding or a skid condition,a brake actuating system utilized to influence the rotational speed ofall said wheels comprising means for actuating the same, means forsensing the rotational speed of each wheel and for generating a signalrepresenting the same, means for amplifying and transmitting each signalto valve means for separately controlling the application and reductionof brake effort to each portion of the braking system associated witheach wheel, the improvement comprising means for sensing the differencesin rotational speeds of each of the wheels, means for electricallycommunicating the sensed information to said valve means for selectivelyincreasing and decreasing brake effort to each of the wheels as afunction of the information received for varying the rotational speedsof said wheels, such that said valve means are selectively activated forapplying brake pressure to any of the driven wheels in an overspeedingcondition, and are selectively activated for reducing brake pressure toany of the wheels rotating at a speed substantially less than that ofthe fastest wheel, said valve means comprising means for directing thebrake pressure produced at any such wheel to be applied through saidbrake actuating system to increase the brake pressure to all of theother wheels, means connecting said brake actuating system and saidsensing and communicating means for actuating said means for reducingpressure only when said brake actuating system is actuated, each saidvalve means consisting of communicating lines from the brake circuit ofthe vehicle and from the brake pedal, and piston and circuit means forreceiving pressure from a locked or relatively slowly rotating wheel andbeing directly responsive thereto for increasing the brake pressure inthe line communicating with the brake pedal and the other wheels.